Perhaps it is no more dangerous than any other memory/fs configuration
BS. If you save the few bucks for reliable DRAM then ZFS is EVEN BETTER! That's the simple truth.
If you run regular scrubs (recommended and default with OMV, FreeNAS and most probably any other good NAS appliance) your filesystem will tell you if you have bad memory. Since it will report data corruption having happened. Then at least you start to know what ECC memory is for (another step to prevent data corruption).
If you don't run scrubs (really stupid idea) on a system with non-ECC memory still ZFS (or btrfs) does a better job compared to anachronistic filesystems since now bit flips that affect filesystem structures are much less likely to happen as on the same system with a non-checksumming filesystem like ext4.
It's still as easy as: use ECC DRAM whenever possible and use a checksumming filesystem whenever possible. At least if you love your data and hate bit rot. If you don't care about your data and think silent data corruption is fine you are free to use anything (since it doesn't matter to you anyway).
Again: please stop spreading such BS like 'ZFS can/should only be used with ECC DRAM'. It's quite the opposite! Please take your time and read carefully through http://jrs-s.net/2015/02/03/wi…n-ecc-ram-kill-your-data/